We hypothesize that response to a single test done of GnRH agonist Lupron will distinguish between gonadotropin deficiency (GnD) and constitutional delay of puberty (CDP) better than sleep or GnRH (Factrol) tests. Secondary hypothesis: Optimally spaced series of Lupron injections will distinguish hypothalamic from pituitary causes of GnD. Pilot studies will be carried out in normal adult men & women 18-35 years of age. Major test pop. will be teenage boys & girls who are normal volunteers or have delayed puberty shown to be GnD or CDP.